The invention is based on a hand power tool.
From European Patent Disclosure EP 350 855, a commutator for a universal motor is known, of the kind also provided for hand power tools. Its laminations have the outer contour of a low rectangle whose short sides have U-shaped openings into which an annular armature that bundles the laminations together in ringlike fashion can be placed. The laminations are also shaped in the form of bars and, at the operating speed of approximately 3000 rpm of the electric motor that carries the commutator, they are subjected to relatively strong forces that bend the individual laminations outward and cause the commutator, on its outside oriented toward the carbon brushes, not to have a flat, cylindrical contour but rather to have the tendency of having a curved convex contour. As a result, the contact area between the arched outside of the commutator and the flat carbon brushes is reduced considerably, resulting in increased spark development between the carbon brushes and the commutator; both the commutator and the carbon brushes suffer considerable wear or damage from the high temperatures in the arc.
In known commutators of hand power tool motors, the attempt has been made to counteract their deformation at high rpm by means of annular armatures, which keep the annularly bundled laminations that form the commutator prestressed radially inward. This arrangement has had only partial success, and despite the provisions described the known commutators are only inadequately secured against deformation and are relatively complicated and expensive to produce and install.